The present invention relates to volumetric infusion pumps for the administration of intravenous (IV) fluids to a patient. More particularly, the invention relates to a disposable soft manifold and pump cassette for supplying a plurality of solutions to one or more intravenous tubes.
Intravenous infusion therapy involves the administration of medications and other fluids directly into the circulatory system of a patient. Infusion pumps are typically used to regulate the delivery of these medications and fluids with a high degree of accuracy. Medical treatment frequently requires the administration of more than one solution or medication to an individual patient. In many medical treatments, several drugs are administered sequentially or periodically. Alternatively, a patient may need a particularly large volume of a single infused liquid requiring more than one supply vessel, or may need to have two or more different solutions delivered in rapid succession, solutions which would lose their efficacy if mixed.
In early attempts to administer multiple fluids to a patient, plural independent gravity flow controllers and plural independent electronic pumps have been employed. Both of these methods of administering multiple fluids to a patient have significant disadvantages. For example, both methods require the use of multiple IV tubes to administer the fluids, resulting in multiple IV venipuncture and a corresponding increased risk of infection. Also, both the plural gravity flow controller method and the plural electronic pump method result in considerable increased clutter around the patient and increased time and labor by the health care practitioner to set up and operate. Plural gravity flow controllers have the additional disadvantage of being prone to inaccuracies due to tube occlusion or shape changes. Likewise, plural independent pump methods have additional disadvantages including the high cost of maintaining several pumps for each patient, and of maintaining an inventory of tubes that must be replaced periodically to avoid infection.
The prior art has employed several methods in attempts to overcome these mentioned difficulties. Many of the prior art methods involve the use of disposable cassettes or manifolds with multiple fluid inlet channels to accommodate a plurality of solutions. However, these prior art disposable cassettes and manifolds have their own disadvantages which the present invention overcomes.
Epstein et al., U.S. Pat. No. 4,696,671, discloses an infusion system for administering multiple infusates at individually programmable rates and sequences. In Epstein, a disposable cassette with plural fluid input ports and one fluid output port is provided. All fluids flow through this unitary disposable cassette without making any other system contact. The multiple input port disposable cassette disclosed in Epstein eliminates many of the difficulties discussed above, including the risk of infection due to multiple IV punctures since only a single IV puncture is necessary. The Epstein cassette also eliminates some of the increased time, labor, and cost required to maintain multiple gravity flow controllers or independent electronic pumps.
However, the construction of the disposable cassette disclosed in Epstein has disadvantages as well. This design involves rigid injection molded parts. The rigid molded construction introduces several disadvantages. First, the rigid construction results in higher labor and assembly costs, which increases the cost to the health care consumer. A second disadvantage of the disposable cassette disclosed in Epstein relates to the control of fluid flow through different input ports. Cassettes of this type typically employ solenoid valves or motor-driven actuators to pinch off tubing in a sequential manner in order to restrict or control fluid flow. Pinching off the rigid tubing disclosed in Epstein requires considerable force, and consequently considerable energy. In addition to being energy inefficient, these forces can also have an adverse affect on the tubing integrity with repeated close ups. Finally, the configuration of the disposable cassette disclosed in Epstein requires more labor in assembly and replacement than the industry desires, raising the cost to health care consumers.
A second approach is described in Wunsch, U.S. Pat. No. 4,512,764. Wunsch discloses a three-piece manifold valve assembly infusion system capable of administering multiple solutions to a patient through a single supply tube. The manifold valve assembly includes a disposable tubing manifold with a single flexible trunk tube and a plurality of flexible branch tubes. Each flexible branch tube is connected to the flexible trunk tube on one end, and to a solution to be administered on its other end. The single flexible trunk tube is connected to a single intravenous supply catheter so that multiple solutions may be sequentially dispensed to the patient. Valves in the manifold valve assembly selectively engage each flexible branch tube, closing all but one branch tube at any one time, to prevent fluid flow through these branch tubes.
The Wunsch tubing manifold overcomes many of the problems associated with delivering multiple solutions to a patient, as well as some of the disadvantages of the disposable cassette disclosed in Epstein et al. For example, the flexibility of the trunk tube and branch tubes disclosed in Wunsch allows the tube paths to be pinched off with less force than is required in Epstein. This fact results in a more energy efficient system, since less energy is required to operate the valve mechanism. However, the disposable tubing manifold disclosed in Wunsch has disadvantages of its own. First, because of the necessary connections of flexible plastic tubing, the Wunsch manifold is difficult to fabricate. Second, because of the increased complexity in fabrication, the Wunsch flexible tubing manifold has increased costs associated with its manufacture. Finally, the tubing manifold disclosed in Wunsch requires more labor by the health care practitioner to replace than is desired in the industry.
Although the Wunsch and Epstein et al. patents attempt to meet the need for a system capable of administering multiple fluids to a patient through a single catheter supply tube, each of these disclosed methods has its own shortcomings and fails to satisfy a need in the infusion system market. The AVI pumping cassette, disclosed in U.S. Pat. Nos. 4,382,753 and 4,236,880, is the most reliable, accurate and potentially the most cost-effective disposable pumping cassette in the market place. However, it is designed to deliver a single IV solution to a patient at any one time.